The present invention relates to the production of mineral ore, particularly from low-grade ore bodies. The mineral ore such as iron ore is recovered from an aqueous slurry via a flotation process.
Mineral ores such as iron ore are obtained from deposits referred to as either high or low-grade deposits. Froth flotation is a process for recovering and concentrating minerals from ores. In a froth flotation process, the ore is wet ground to obtain a pulp. Additives such as collector agents, frother agents, depressants, activators, etc. are added to the pulp to assist in separating valuable minerals from undesirable gangue portions of the ore in subsequent flotation steps. The pulp is then aerated to produce a froth at the surface. The materials which adhere to the bubbles or froth are collected as concentrates. Selective suppressants or depressants inhibit the adhesion of the certain minerals to the bubbles or froth, thus assisting in the separation of the froth products from the desirable products which can include those minerals suppressed by the suppressant agent. The froth product or the reject product or both can then be further processed to obtain the desired minerals, such as by additional flotation stages. Generally, the ore is initially floated to produce a rougher concentrate, the rougher concentrate thereafter being re-floated in the presence of suppressants or collector agents to further separate the minerals therein. Typical mineral flotation collector agents include sulfydryl collector agents such as xanthate and fatty acid based collector agents such as sodium oleate.
The present invention provides a process for the selective separation of ore values when a ground mineral ore containing gangue material is first dispersed in an aqueous medium and thereafter conditioned with an effective amount of a treatment reagent whereby the recovery of ore from a froth flotation process is increased. The treatment reagent of the present invention is a water-soluble organophosphonate which is used alone or preferably in combination with a polymeric dispersant.
In accordance with the present invention, there is provided a method of improving the separation of mineral values from their associated gangue. The present invention will be described with respect to flotation recovery of iron ore values from its associated gangue. It is believed that this method is also compatible with other ore recovery systems wherein mineral values are selectively separated from their associated gangue. The method itself involves the addition of an effective amount of a treatment reagent to the froth flotation process which enhances the ore recovery. By xe2x80x9ceffective amountxe2x80x9d of the reagent it is meant that amount of the reagent that is effective in producing the desired degree of increase in the recovery of ore values. The particular amount that is effective will vary depending upon variables such as the particular ore processed, the specific composition of the reagent, etc. Therefore, a precise statement as to the effective amount is not possible. Generally however, the effective amount will arrange from about 0.1 to 100 parts per million reagent in the ore flotation feed slurry.
The treatment reagents of the method of the present invention comprise water-soluble organophosphonates which when added to the flotation feed slurry enhance the recovery of ore values therefrom. Examples of acceptable organophosphonates include hydroxyethylidenediphosphonic acid (HEDP), diethylenetriamine penta-(methylene phosphonic acid) (DETA), aminotri(methyphosphonic acid) (AMP), hexamethylenediaminetetra(methyphosphonic acid) (HMDTMP), ethylenediaminetetra(methylenephosphonic acid) (EDTMP), 2-phosphonobutane-1,2,4-tricarboxylic acid (PBTC), hydroxypropyldiphosphonic acid (HPDP) or blends thereof. Such organophosphonates may be added to the systems in an amount of from about 0.1 to about 100 parts per million. The organophosphonate treatment reagent may be used alone or in combination with a polymeric dispersant.
Suitable polymeric dispersants within the scope of the present invention comprised water-soluble polymers having the structure: 
wherein R1 is H or lower alkyl (C1-C3): R2 is OH or OM, or NH2; M is a water-soluble cation, R3 is a hydroxy substituted alkyl or alkaline radical having from 1 to 6 carbon atoms or a nonsubstituted alkyl or alkylene radical having from 1 to 6 carbon atoms; X, when present, is an anionic radical selection from the group consisting of SO3, PO3, PO4, and COO, Z when present, is H or hydrogens or any water soluble cation or cations which together counterbalances the valence of the anionic radicals, a is 0 or 1.
The number average molecular weight of the water-soluble copolymers of Formula I may fall within the range of 1,000 to 1,000,000. Preferably the number average molecular weight will be within the range from 1,500 to 500,000 with the range of about 1,500 to about 10,000 being even more highly desirable. The key criterion is that the polymer be water-soluble.
The molar ratio x:y of the monomers of Formula 1 may fall within the range of between about 30:1 to 1:20, with the x:y molar ratio range of from about 10:1 to 1:5 being preferred.
At present, the water-soluble polymer preferred for use in the present invention is: 
wherein M is the same as given in Formula 1. This polymer (Formula II) is referred to as acrylic acid-/allyl hydroxy propyl sulfonate ether (AA/AHPSE). The IUPAC nomenclature for AHPSE is 1-propane sulfonic acid, 2-hydroxy-3-(2-propenyl oxy)-mono sodium salt.
The treatment reagent used in the method of the present invention is added to the ore flotation feed slurry, preferably as an aqueous solution. The treatment reagent can be added to the ore flotation feed slurry to provide a concentration of from about 0.1 to 100 parts per million, preferably from about 1 to 10 parts per million in the treatment slurry. When a combination of organophosphonate and polymeric dispersant is employed, the ratio of organophosphonate to polymeric dispersant can range from about 20 to 1 to about 1 to 5, preferably about 5 to 1.
The present invention will now be further described with reference to a number of specific examples which are to be regarded as illustrative and not as restricting the scope of the present invention. All percentages stated herein are by weight.